This invention is directed to assay devices for determination of characteristics of samples, unitized housings, and kits incorporating the test strips and housings, and methods of determining the characteristics of samples using test strips and housings, in which the test strips and housings employ detachable components.
Among the many analytical systems used for detection or determination of analytes, particularly analytes of biological interest, are chromatographic assay systems as well as other assay systems employing test strips for detection or determination of analytes.
Among the analytes frequently assayed with such systems are:
(1) hormones, such as human chorionic gonadotropin (hCG), frequently assayed as a marker of human pregnancy; PA0 (2) antigens, particularly antigens specific to bacterial, viral and protozoan pathogens such as Streptococcus, hepatitis virus, and the protozoan Giardia, a frequent cause of diarrhea; PA0 (3) antibodies, particularly antibodies induced as a result of infection with pathogens, such as antibodies to the bacterium Helicobacter pylori and to human immunodeficiency virus (H.I.V.), suspected to be the cause of AIDS; PA0 (4) other proteins, such as hemoglobin, frequently assayed in determinations of fecal occult blood, an early indicator of gastrointestinal disorders such as colon cancer; PA0 (5) enzymes, such as aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, and glutamate dehydrogenase, frequently assayed as indicators of physiological function and tissue damage; PA0 (6) drugs, both therapeutic drugs, such as antibiotics, tranquilizers, and anticonvulsants, and illegal drugs of abuse, such as cocaine, heroin, marijuana, and methamphetamine; PA0 (7) environmental pollutants such as pesticides and aromatic hydrocarbons; PA0 (8) vitamins; and PA0 (9) other physiologically important compounds such as cholesterol, whose concentration is symptomatic of health or disease states. PA0 (1) a first opposable component including: PA0 (2) a second opposable component hingedly attached to the first opposable component. PA0 (1) the assay device described above; and PA0 (2) a test strip backed with adhesive and a releasable liner for insertion into the second receptacle of the assay device. The test kit can further comprise, separately packaged, at least one additional reagent for application either to the sample collection device or the test strip. The additional reagent can form an extraction reagent when applied to the sample collection device. The extraction reagent formed can be nitrous acid. PA0 (1) collecting a sample on a sample collection device; PA0 (2) inserting the sample collection device containing the sample into the first receptacle of the assay device described above; PA0 (3) removing a releasable liner from a test strip backed with adhesive and a releasable liner and inserting the test strip from which the releasable liner has been removed into the second receptacle of the assay device; PA0 (4) bringing the first and second opposable components of the assay device into opposition to express fluid from the sample collection device for application to the test strip; and PA0 (5) observing or measuring a detectable signal produced on the test strip in response to fluid applied to it in order to detect or determine the analyte on the test strip. PA0 (1) a first opposable component including: PA0 (2) a second opposable component hingedly attachable to the first panel of the first opposable component, the second opposable component including therein an aperture; and PA0 (3) a third opposable component hingedly attachable to the second opposable component, the third opposable component including a second receptacle for a test strip. PA0 (1) a first module comprising: PA0 (2) a second module including therein a second receptacle for a test strip, the second module reversibly hingedly attachable to the second panel of the first module. PA0 (1) a first support panel including thereon a sample preparation zone; PA0 (2) a second support panel hingedly attached to the first support panel and including therein an aperture, the second support panel shaped to have first, second, third, and fourth sides with the first and third sides being substantially parallel and the second and fourth sides being substantially parallel, with the first side being hingedly attached to the first support panel; PA0 (3) a third support panel hingedly attached to the third side of the second support panel, the third support panel having first and second surfaces with a test strip attached to the second surface; PA0 (4) a first reaction panel hingedly attached to the second side of the second support panel having thereon a first reaction pad; and PA0 (5) a second reaction panel hingedly attached to the fourth side of the second support panel having thereon a second reaction pad. PA0 (1) a first module including: PA0 (2) a second module comprising a third support panel, the third support panel including thereon a test strip, the second module being removably hingedly attachable to the third side of the second support panel of the first module; PA0 (3) a third module that is a first reaction panel that has a first reaction pad thereon and that is removably hingedly attachable to the second side of the second support panel of the first module; and PA0 (4) a fourth module that is a second reaction panel that has a second reaction pad thereon and that is removably hingedly attachable to the fourth side of the second support panel of the first module. PA0 (1) a first support panel including thereon a sample preparation zone; PA0 (2) a second support panel hingedly attached to the first support panel and including therein an aperture, the second support panel shaped to have first, second, third, and fourth sides with the first and third sides being substantially parallel and the second and fourth sides being substantially parallel, with the first side being hingedly attached to the first support panel; PA0 (3) a third support panel hingedly attached to the third side of the second support panel, the third support panel having first and second surfaces and having a receptacle for a test strip such that, when a test strip is inserted into the receptacle, a surface of the test strip is accessible from the second surface of the third support panel; PA0 (4) a first reaction panel hingedly attached to the second side of the second support panel having thereon a first reaction pad; and PA0 (5) a second reaction panel hingedly attached to the fourth side of the second support panel having thereon a second reaction pad. PA0 (1) a first module including: PA0 (2) a second module comprising a third support panel, the third support panel having first and second surfaces and having a receptacle for a test strip such that, when a test strip is inserted into the receptacle, a surface of the test strip is accessible from the second surface of the third support panel, the second module being removably hingedly attachable to the third side of the second support panel of the first module; PA0 (3) a third module that is a first reaction panel that has a first reaction pad thereon and that is removably hingedly attachable to the second side of the second support panel of the first module; and PA0 (4) a fourth module that is a second reaction panel that has a second reaction pad thereon and that is removably hingedly attachable to the fourth side of the second support panel of the first module. PA0 (1) a first opposable component including: PA0 (2) a second opposable component hingedly attached to the first opposable component.
Such chromatographic systems and other assay systems involving test strips are frequently used by physicians and medical technicians for rapid in-office diagnosis and therapeutic monitoring of a variety of conditions and disorders. They are also increasingly used by patients themselves for at-home monitoring of such conditions and disorders.
Among the most important of such systems are the "thin layer" systems in which a solvent moves across a thin, flat absorbent medium. Among the most important of tests that can be performed with such thin layer systems are immunoassays, which depend on the specific interaction between an antigen or a hapten and a corresponding antibody. The use of immunoassays as a means of testing for the presence or amount of clinically important molecules has been known for some time. As early as 1956, J. M. Singer reported the use of an immune-based latex agglutination test for detecting a factor associated with rheumatoid arthritis (Singer et al., Am. J. Med. 222: 888-892 (1956)).
Among the chromatographic techniques used in conjunction with immunoassays is a procedure known as immunochromatography. In general, this technique uses a disclosing reagent or particle that has been linked to an antibody to the molecule to be assayed, forming a conjugate. This conjugate is then mixed with a specimen, and if the molecule to be assayed is present in the specimen, the disclosing reagent-linked antibodies bind to the molecule to be assayed, thereby giving an indication that the molecule to be assayed is present. The disclosing reagent or particle can be identifiable by color, magnetic properties, radioactivity, specific reactivity with another molecule, or another physical or chemical property. The specific reactions that are employed vary with the nature of the molecule being assayed and the sample to be tested.
Immunochromatographic assays fall into two principal categories: "sandwich" and "competitive," according to the nature of the antigen-antibody complex to be detected and the sequence of reactions required to produce that complex. The antigen to be detected can itself be an antibody, such as in serological assays for H. pylori-specific antibody. In such cases, the antibody to be detected can be bound to a specific antigen. Alternatively, the antigen to be detected can be detected indirectly by using a labeled second antibody that binds to the first antibody to the antigen to be detected.
In general, the sandwich immunochromatographic procedures call for mixing the sample that may contain the analyte to be assayed with antibodies to the analyte. These antibodies are mobile and typically are linked to a label or a disclosing reagent, such as dyed latex, a colloidal metal sol, or a radioisotope. This mixture is then applied to a chromatographic medium containing a band or zone of immobilized antibodies to the analyte of interest. The chromatographic medium often is in the form of a strip resembling a dipstick. When a complex of the molecule to be assayed and the labeled antibody reaches the zone of the immobilized antibodies on the chromatographic medium, binding occurs, and the bound labeled antibodies are localized at the zone. This indicates the presence of the molecule to be assayed. This technique can be used to obtain quantitative or semi-quantitative results.
Examples of sandwich immunoassays performed on test strips are described by U.S. Pat. No. 4,168,146 to Grubb et al. and U.S. Pat. No. 4,366,241 to Tom et al., both of which are incorporated herein by this reference.
In competitive immunoassays, the label is typically labeled analyte or analyte analogue which competes for binding to an antibody with any unlabeled analyte present in the sample. Competitive immunoassays are typically used for detection of analytes such as haptens, each hapten being monovalent and capable of binding only one antibody molecule. Examples of competitive immunoassay devices are those disclosed by U.S. Pat. No. 4,235,601 to Deutsch et al., U.S. Pat. No. 4,442,204 to Liotta, and U.S. Pat. No. 5,208,535 to Buechler et al., all of which are incorporated herein by this reference. Other forms of competitive immunoassays exist using labeled antibody.
Although useful, currently available chromatographic techniques using test strips have a number of drawbacks. Many samples, such as fecal samples, contain particulate matter that can clog the pores of a chromatographic medium, greatly hindering the immunochromatographic process. Other samples, such as blood, contain cells and colored components that make it difficult to read the test. Even if the sample does not create interference, it is frequently difficult with existing chromatographic test devices to apply the sample to the chromatographic medium so that the sample front moves uniformly through the chromatographic medium to ensure that the sample reaches the area where binding is to occur in a uniform, straight-line manner. Similar problems occur with other assay methods employing test strips that do not employ immunochromatography.
Other problems exist with currently-available test strips because of the nature of the sample to be assayed or the assay to be carried out. With such devices, it is impractical to perform washing steps which are frequently desirable to improve sensitivity and to reduce background. Also, it is difficult, and in many cases impossible, to carry out preincubation steps within the device or incubation steps for development of a detectable signal such as that produced by an enzyme label.
Additionally, there is a need for an immunochromatographic assay device that can carry out a broad range of separations as well as similar devices for the performance of other assays not involving immunochromatographic principles.
Sample preparation and waste generation are responsible for other problems with currently-available devices and techniques for immunochromatography and other currently-available test strips. The increased prevalence of diseases spread by infected blood and blood fractions, such as AIDS and hepatitis, has exacerbated these problems. It is rarely possible to apply a sample (such as feces) or a sampling device (such as a throat swab) directly to the chromatographic medium or other test strip. Several extraction and pretreatment reactions are usually required before the sample can be applied to the chromatographic medium or the test strip. These reactions are typically carried out by the physician or technician performing the test in several small vessels, such as test tubes or microfuge tubes, requiring the use of transfer devices, such as pipettes. Each of the vessels and transfer devices is then contaminated and must be disposed of, using special precautions so that workers or people who may inadvertently come into contact with the waste do not become contaminated.
Still another limitation on chromatographic devices currently available for use by the clinician or technician is their inability to perform two-directional chromatography. This technique has long been known to be a powerful analytical tool, but its complexity, relative to simple unidirectional chromatography, has made it difficult to apply it to test strip devices in the physician's office or clinical laboratory.
Additional considerations arise from storage requirements for currently available devices. It is well known by those skilled in the art that moisture is detrimental to the stability of an immunochromatographic test device. Therefore, a means of maintaining a low humidity environment is necessary. The entire test device, consisting of the housing and its attached components, is sealed in a barrier bag which is essentially moisture impermeable. Typically, a desiccant such as silica gel, "molecular sieves," or clay-based derivatives is also sealed with the device in order to scavenge residual moisture released by the device itself or moisture which may permeate the barrier over time.
From a functionality standpoint, only the biologically reactive components require a low humidity environment. The non-biologically active components of such a device do not require such an environment. Sealing the entire test device in a low humidity environment is not done out of necessity, rather out of convenience. However, convenience exacts a price. The moisture barrier component must be sufficiently large to accommodate the entire test device. This increases the final package dimensions of test kits incorporating these devices and increases the volume of desiccant required.
In addition to increased packaging and its associated costs, other prices are to be paid for the convenience of a single, unitary device. Assembly times are increased when a test strip containing biologically active components is applied to a housing. The increased time is inversely related to manufacturing throughput and directly related to the cost of the finished test. If the housing is comprised of a material capable of high residual moisture levels, e.g., a cellulosic material such as cardboard, procedures are required to reduce the residual moisture to acceptable levels thereby again increasing manufacturing costs. Also, moisture reduction requires specialized equipment which must be purchased, operated, and maintained, again increasing cost.
Accordingly, there is a need for an improved assay device capable of handling a broad range of chromatographic assays and other assays employing test strips. Such a device should be able to handle all types of immunoassays, including both sandwich and competitive immunoassays, as well as other types of assays using chromatography and other assays involving test strips. Such a device should be capable of receiving a possibly contaminated sample or a sample preparation device directly so as to eliminate the need for extraction vessels and transfer devices. Such a device, preferably in the form of a test strip, should also be capable of performing immunochromatographic assays on colored samples or samples containing particulates without interference and should be able to deliver the sample to the chromatographic medium uniformly and evenly to improve accuracy and precision of the test. Additionally, such an improved test strip should be capable of performing bidirectional chromatography when used in clinical laboratories or physicians' offices. Moreover, such an improved assay device should reduce packaging and storage costs and the volume of desiccant required for storage.